In an analog television, a composite video signal of an image comprises a luminance signal (Y) and a chrominance signal (C). A comb filter is commonly used to separate the luminance signal and the chrominance signal from the composite video signal. The process of separating the luminance signal and the chrominance signal is referred to as a Y/C separation.
An image sharpness processing for the luminance signal is capable of enhancing edges of an image, that is, the image can become clearer. Generally speaking, the image sharpness processing is to add a sharpness signal to the luminance signal. The sharpness signal is obtained according to the luminance signal. However, when the edges of the image are enhanced, a noise is also enhanced and quality of the image is affected.
Therefore, there is a need for a solution to avoid the problem that when the edges of the image are enhanced, the noise is also enhanced.